This invention relates to fuel dispensing nozzles, and more particularly to apparatus for limiting the rate of flow of fuel through a fuel dispensing nozzle such that it is prevented from exceeding a preselected maximum flow rate.
Fuel dispensing nozzles are commonly used to dispense gasoline or other fuels into fuel tanks of motorized vehicles. Conventional dispensing nozzles include a nozzle body defining an internal flow passage extending between the nozzle inlet and its outlet. The inlet of the nozzle is connected to a supply hose which feeds pressurized gasoline or other fuel to the nozzle. This pressurized fuel passes through the internal flow passage to an outlet which consists of, or is connected to, a spout which serves as the discharge end of the nozzle. The spout is inserted into the neck of a motorized vehicle's fuel tank during filling operations. The pressurized fuel flow through the internal fuel passage is conventionally controlled by a valve which is actuated by a manually operated valve lever selectively depressed by the nozzle user during dispensing operations.
Fuel, under pressure created by a pump, is fed through the nozzle at flow rates established by the pump capacity and the extent to which the valve lever is actuated. It has been found that the rapid flow rates capable of being generated by conventional fuel pumps feeding the nozzle produce gasoline or other fuel fumes which escape into the atmosphere. Due to the wide spread use of dispensing nozzles and the volume of fumes escaping during dispensing operations, government regulations have been proposed which are designed to limit the rate of flow of fuel through the dispensing nozzle. By limiting the rate of flow, the amount of fumes escaping can be reduced to a level which is less likely to cause significant damage to the earth's atmosphere.
In our aforesaid copending patent application a fuel dispensing nozzle such as those at gasoline service stations and the like proposed a flow restriction device within the body of the nozzle, the device creating turbulence which provides a resistance to flow so that the delivery rate could not exceed a predetermined maximum despite variations within a range of supply inlet pressures. Inherent in that apparatus is a predictability of flow pattern at the point of use of the device in order to provide a margin of accuracy in the determination of the predicted maximum rate in the prevailing environment of use including extreme variations in delivery pressure, specific maximum rates imposed by regulatory agencies, and the necessity to approximate those maximum rates in order to provide maximum utilization of the petroleum industries distribution equipment. For example, one of the problems in limiting the fuel flow through a fuel nozzle is that the fuel inlet pressure varies considerably at the various dispensing stations, e.g., the fuel inlet pressure may vary between approximately 8 psi and above 55 psi. If a small diameter nozzle outlet were utilized, and if a 10 gallons per minute level were to be established at 55 psi, then at an 8 psi station the flow through the nozzle would be too low from a practical standpoint. If the 10 gallons per minute limitation were established at 8 psi, then the flow rate would be excessive at a station pumping at 55 psi.
Accordingly, the apparatus of the aforesaid patent application placed a turbulence creating member within the nozzle between the inlet and the valve so as to restrict and limit the fuel flow to a predetermined maximum rate irrespective of the inlet pressure within the 8 psi to 55 psi range and irrespective of the amount that the valve is opened. It was found that as the fuel passage within the nozzle is blocked, a turbulent flow occurred which hindered the flow of the fuel through the nozzle, and as the inlet pressure increased within the range, the turbulence increased in a non-linear fashion resulting in a type of feedback which further retarded the flow and maintained the flow at a maximum level. Thus, the flow control mechanism maintained the flow constant within the range of inlet pressures. In order to obtain predictable results the turbulence generating means in our aforesaid copending patent application had to be disposed upstream of the valve so that it received the fuel in a substantially laminar flow condition. The laminar flow upstream of the turbulence generating means results from several feet of hose attached to the inlet to the nozzle. The valve itself creates a turbulence to the flow of fuel and if the valve were disposed upstream of the turbulence generating means, unpredictable fuel rates would result. The reason for this is that present valve designs provide a valve chamber at some angle to the flow passage through the nozzle. The valve comprises a spring urged "bonnet" valving means mounted on a long push-rod type valve stem and includes a skirt portion which both guides the bonnet when it is urged closed and also tends to restrict flow past the bonnet thereby providing more sensitive control to the operator. In many instances the valve bonnet is adapted to angularly disorientate or tilt during the initial opening or just prior to closing to provide a "penny-pincher" mode such as described in U.S. Pat. No. 3,330,479. The direction of slant or tilt of the valve bonnet in this mode is random. Further, the amount and direction of eccentricity of the skirt of the bonnet within the valve chamber is a function of the pressure against the bonnet, the loading on the spring, and the amount of wear on the valve stem packing. The flow path of liquid downstream of the manually operated valve, at any specific flow rate, is therefore random and unpredictable. Thus, the turbulence generating means was disposed intermediate the inlet and the valve.
However, many fuel service or filling stations presently utilize swivel mechanisms such as that disclosed in U.S. Pat. Nos. 2,745,682 and 3,558,163 and additionally swivel/breakaway mechanisms such as that disclosed in U.S Pat. No. 4,791,961, such mechanisms being being proximate the entry to the nozzle and between the hose and the nozzle. These devices vary in design and flow characteristics, not only from device to device, but also from one specific flexure position to another, within the same device. Accordingly, the flow of fuel into the inlet of the nozzle may not be laminar, but would have turbulent characteristics, in which case the desired predictability and control of fuel flow rate may not be attained.